Steam separator



Oct. 25, 1949. w s, PATTERSON 2,485,767

STEAM SEPARATOR Filed Dec. '50, 1944 2 Sheets-$heet 1 IN V EN TOR. M/ard5. Pa zzerson Oct. 25, 1949. w. s. PATTERSON STEAM SEPARATOR 2Sheets-Sheet 2 Filed Dec. 50, 1944 v INVENTOR.

Marc! SPazzaraon Patented Oct. 25, 1949 UNITED S TAT'ES PATENT O F-l'C-ESTEAM SEPARA'IOR Ward S. Patterson, 'Chappaqua, N. Y., assignor .toCombustion Engineering-Superheater, Inc., a corporation of DelawareApplication December 30, 1944, Serial No. 570,555

4 Claims. 1

This invention relates to separators and particularly to the separationof moisture from steam within .the drum of a steam boiler.

In a water-tube boiler of the natural circulation type and in someforced circulation boilers, onlypart of the water passing through theheated tubes is evaporated into steam to travel along with the water asa more or less heterogeneous mixture. The steam must then be separatedfrom the Water, and the Water recirculated with fresh feed water throughthe boiler tubes. This separation must be accomplished in such anefiicient manner that the steam is practically dry or free of entrainedmoisture, because any moisture carried with the steam also carries withit dissolved and suspended solids, which, on evaporation of the water,become deposited on the internal surfaces of the superheaters, onturbine blades, or in valves, etc., Where it is very objectionable.

In steam generating units it has been found that up to a certain outputof steam the steam is dry but if this output is exceeded the moisture inthe steam increases rapidly. The maximum output at which commerciallydry steam 'is obtainable is a function of the drum pressurathe steamspace in the boiler drums, the character of *the boiler water and thetype of boiler. In an article entitled Boiler capacity has outgrown itsterminology published in Combustion of March- 1934, page 11, the chartdesignated Fig. 1 shows the steam liberation in cubic feet and pounds ofsteam per hour at various pressures for each cubic foot of steam spacein the separation drum of a number of boilers. the limitations of thesteaming capacities of drums at that time. It is shown that in a drumnot equipped with separating devices steaming capacities generallyfollow a law for the settling velocities of particles of moisturefalling through the steam. Since then various attempts have been made toimprove those liberations by installing apparatus of various typeswithin the drum with more or less success.

An object of this invention is to provide im- 1 proved means for theseparation of moisture from steam within the steam space of a boilerdrum.

' Figure 1 is a transverse sectional view through a steam and Water drumof a steam boiler showing one embodiment of the invention, as viewed online |l of Fig. 2;

Figure 2 is a partial longitudinal section through the drum taken online 2-2 of Fig. 1; and

Figures 3 and. 4 are transverse sections, similar This will aid invisualizing ,4

to'Fig. 1, ofother embodiments of the invention.

Figure 1 illustrates the .principal features of the device as applied toa boiler drum in which all of the steam enters the steam space above thewater level. The steam and water drum I0 is provided with tube openingsll through which the steam and water mixtureis discharged from the tubesI2 into the drum. An imperforate bafile l3 opposite and close to thetube openings ll directs the mixture of steam and water downwardlythrough a discharge opening l4 formed by the space between bafile l3 andshell I0. The area of discharge opening I 4 is selected to give arelatively high discharge velocity. Baille I3 is positioned in downwardand outward inclination to cause the discharge of the steam-watermixture in the form of a sheet directed against the drum she'll atapproximately location A above the water line. The density of the wateris much greater than that of the steam so that a heterogeneous mixtureno longer exists because as the denser water is thrown against the drumshell the less dense steam is displaced toward the center of the drumthereby causing a primary separation of water and steam. This separationis accomplished in a very small space between discharge opening 14 andlocation A. To prevent depression of the water level B at a locationdirectly below discharge opening I4 where the steam and water leavingsaid opening would strike the drum at high velocity, a funnel-shaped orconvergent throttling throat I5 is preferably provided. This throat isJformed by plates I6 and drum Ill. Plate T6 is preferably adjustablymovable along the surface of plate ll so as to vary the size of thethroat formed between the outer edge of plate l6 and drum I'll. 'Byvarying the size of throat l5 the amount of water flowing therethroughmay be controlled. The water discharging through opening I l andseparated from the steam may then pass through throat I 5 or spill overthe top edge of bafile plate [7. It has been found that under certainconditions of steam pressure and density satisfactory results may beobtained by omitting plates [6 and I1 and allowing the water dischargedfrom opening [4 to jet directly into the water within the drum and alsothat the screen "2'2 may be omitted. The steam and any entrainedmoisture not yet separated therefrom passes toward the center of thedrum through the opening 1 8 between the bottom of battle I3 and the topof plate 11 -or the water level and passes into space 20 toward screens2|. Any steam entrained with the "water and passing downwardly throughthe throat :l5 rises through Submerged 23 extending to drum I serves asa darn which deflects water flowing against it from above along the drumshell upwardly thereby insuring that all submerged steam in said waterwill pass upwardly through screen 22 into space 20. A perforate blow-01fpipe 23 is located below and adjacent to the opening between the bottom24 of -bafile 23 and the baflle 25 which may serve as a continuous blowdown. Since the water delivered by the tubes contains a relatively largeconcentration of solids, and is delivered from opening l4 downwardlytoward and in part through the opening just above pipe 26 and since thisconcentrated water has not as yet been admixed with relatively pure feedwater entering through pipe 25a, the location of pipe 26 is mostadvantageous for a blow down. Obviously the blowolf pipe 23 may also belocated submerged within the water between baflle 23 and said surfaceagainst which the flow of the mixture issuing from opening l3 passes.

Screens 2| serve several purposes. They are so selected with respect tofree area that they offer sufficient resistance to the flow of steam toinsure a uniform distribution and uniformly low velocity of the steamwithin the steam space 23. Screens 2| also deliver the steam uniformlyinto space 30 beyond. The screens 2| also offer a relatively largecontact surface that becomes wetted by the v entrained moistureremaining in the steam, thereby removing said moisture and therelatively low velocity over said screens permits the screens to drainaway the moisture. The low velocity in the spaces and 3|] allows arelatively long period of time for settling out of the moisture bygravity, thereby improving the moisture separation efficiency of thesespaces. The steam then passes through screens 3| which have a greaterresistance than screens 20 in order to maintain a uniform distributionand low Velocity of the steam in space 30 and again to provide a largeamount of contact surface for any remaining entrained moisture. Thelarge screens 3| are inclined at a substantial angle from the horizontalto insure good drainage of the moisture from the screens and their lowerends may optionally be submerged in the water. After passing throughscreens 3| which function like screens 2| to uniformly distribute thesteam flowing therethrough, the steam discharges into space 32 prior topassing through screens 33 and thence to steam outlet 34. Screens 33 areinclined from the horizontal and so placed that any remaining moistureextracted by them from the steam and draining down the screens will dropfrom their lowest edge into a zone of relatively low velocity of steamin space 32 so as not to be re-entrained. It will be noticed that afteran effective primary separation in a very small space at the side of thedrum where the steam and water mixture enters, the steam passes throughthe drum through substantially the entire available steam space with aminimum flow velocity.

The drum internals including baffles |3, I6,

I1, 23, and 25 and the screens 2|, 22, 3|, and and 33 extendcontinuously throughout the length of the drum between end plates 35,located beyond the last tube openings adjacent the ends of the drum. Theend plates 35 form enclosures was to confine the flow of the steam to apath around the baflles and through the screens. Obviously the bafflesand the various screens may be assembled in narrow sections as shown inFig. 2, so that they may be removed through the manhole 3B of the drum.

In Figs 3 and 4 part of the steam and water mixture is discharged fromtubes |2a entering the drum below the water level. Part of baflles |3aand I3!) are submerged and the entire bafile spaced from the shell toform a passage confining the mixture and leading it to the opening Me.

In Fig. 3 the mixture is discharged against drum Ill as in Fig. 1. InFig. 4 baflle |3b confines the mixture while directing it upwardlytoward a bafile |3c which in turn directs it. against the other side ofbaffie I31) and toward opening l5. The separation of the steam and waterafter leaving discharge opening |4a in both Figs 3 and 4 occurs in thesame manner as it does in Fig. 1 and thereafter the steam flows towardthe steam outlet 34 as described for Fig. 1.

An actual installation of the drum internals made in accordance withthis invention has shown that at a steam pressure of 800 p. s. i. about1950 pounds of steam per hour have been passed through each cu. ft. ofsteam space and upon leaving the drum contained less than A of 1%moisture. When compared with the 1050 pounds limit shown in Fig. 1 ofthe article referred to above, it shows the output to have increased toThis marked increase is due to a combination of the improvement in thelength of time spent by the steam within the steam space of the drum,thereby permitting more moisture to fall out, the effective primaryseparation within a small space of the steam and water mixture bothabove and below the water level where the mixture enters the drum, andthe subsequent elimination of moisture by its deposit upon therelatively large surface of the several screens which also serve toequalize the flow of steam throughout the steam space. I

What I claim is:

1. In a steam separator having a drum contaming a body of water, tubesconnected to discharge a mixture of steam and water at least in partabove the water level, and a steam outlet; means forming a smoothsurface in said drum located above the water level and remote from saidoutlet; baflle means mounted opposite said tubes and disposed to directsaid steam and water mixture downwardly through the steam space ontosaid surface at an acute angle thereto; means forming a funnel shapedthroat below said surface and extending to a point under the waterlevel; submerged bafile means ofiset toward the center of said drum withrespect to said funnel and extending upwardly from adjacent the bottomof said drum toward the water level; a submerged screen extending fromthe throat of said funnel to adjacent upper end of said second bafflemeans; a second screen extending through the steam space to a pointbelow the water level dividing it into separate chambers; and othersteam separating means mounted intermediate and above said second,screen and the steam ofitalse.

2. In a steam separator having a drum containing a body of water, tubesconnected to discharge a mixture of steam and water at least in partabove the water level, and a steam outlet; means forming a smoothsurface in said drum located above the water level and remote from saidoutlet; baffie means mounted opposite said tubes and disposed to directsaid steam and water mixture downwardly through the steam space onto thesurface of the inner wall of said drum at an acute angle thereto in alocation adjacent said tubes and above the water level; means forming afunnel shaped throat below said surface and extending to a point underthe water level; submerged baffle means offset toward the center of saiddrum with respect to said funnel and extending upwardly from adjacentthe bottom of said drum toward the water level; a submerged screenextending from the throat of said funnel to adjacent upper end of saidsecond baffle means; a second screen extending from said first bafllemeans through the steam space to a point below the water level; andother steam separating means mounted intermediate and above said secondscreen and the steam ofitake.

3. In a steam separator having a drum containing a body of water, tubesconnected to discharge a mixture of steam and water at least in partabove the water level, and a steam outlet; means forming a smoothsurface in said drum located above the water level and extendingtherebelow and remote from said outlet; baffle means mounted oppositesaid tubes and disposed to direct said steam and Water mixturedownwardly through the steam space onto said v surface at an acute anglethereto; submerged baffle means ofl'set toward the center of said drumwith respect to said surface spaced from the bottom of said drum andextending upwardly toward the water level; a screen extending throughthe steam space to a point below the water level dividing it intoseparate chambers;

and other steam separating means mounted intermediate said second screenand the steam ofitake.

4. In a steam separator having a drum containing a body of water, tubesconnected to discharge a mixture of steam and Water at least in partabove the water level, and a steam outlet; means forming a smoothsurface in said drum located above the water level and extendingtherebelow and remote from said outlet; baffie means mounted oppositesaid tubes and disposed to direct said steam and water mixturedownwardly through the steam space onto said surface at an acute anglethereto; submerged baflle means offset toward the center of said drumwith respect to said surface spaced from the bottom of said drum andextending upwardly toward the water level; a screen extending throughthe steam space to a point below the water level dividing it intoseparate chambers; other steam separating means mounted intermediatesaid second screen and the steam ofitake; a submerged feed water inletlocated beyond said second mentioned baffle with respect to saidsurface; and a blow-off pipe submerged within the water between saidsurface and said second mentioned bafile means.

WARD S. PATTERSON.

REFERENCES CITED The following referencesare of record in the file ofthis patent:

UNITED STATES PATENTS Number Name Date 1,946,248 Weigel Feb. 6, 19342,091,421 Sherman Aug. 31, 1937 2,232,256 Place Feb. 18, 1941 2,298,287Frisch Oct. 13, 1942 2,346,672 Fletcher Apr. 18, 1944 2,378,862 PlaceJune 19, 1945

